An MPA is an amplifier that enables output of several hundred to several thousand watts by combining high-frequency signals amplified by a plurality of amplifiers, and is used in systems for transmitting radio waves, such as an electrical communication system and a radar system. The MPA is mounted also on “KIZUNA (WINDS)” satellite, which is in service on orbit as of 2011. By mounting the MPA on a satellite, an antenna beam may be spread without a drive portion. In such satellites and spacecraft, however, high reliability is particularly required for the MPA. Further, the number of redundant amplifiers is limited in view of resource problems.
When high reliability is required for the MPA, it is important to secure reliability in an amplifier part constituting the MPA. Redundancy is one method for improving the reliability. In a system including a plurality of devices of a similar type, such as the MPA, it may be considered to design the devices to have a redundant configuration so that, even when a problem occurs in any of active devices, switching to a stand-by device is perforated to maintain the function of the system. As a simple redundant configuration, one that prepares stand-by devices for all of the active devices may be considered, but such a configuration requires twice as many devices as the active devices, which is not preferred considering resource problems.
Besides, there may be considered a configuration in which stand-by devices fewer than active devices are prepared and connection to an active device having a problem is switched to connection to a stand-by device. In this case, because the active device having a problem cannot be specified before the problem occurs, the stand-by device is required to be substitutable no matter which active device fails.
On the other hand, there is considered a case where an RF signal is divided into a plurality of RF signals by a divider or the like, and the respective divided RF signals are amplified by the MPA and combined by a combiner. At this time, the plurality of RF signals, which has input to the combiner, are each required to have the same amplitude and phase. When the amplifiers are designed to have a redundant configuration, the outputs are each required to have the same amplitude and phase not only when the outputs of the active amplifiers are compared to each other, but also even after a part of the active amplifiers is switched to the stand-by amplifier.
Patent Literature 1 describes a technology involving appropriately determining the electric length of a connection path so as to match a phase obtained through passage of a connection path passing through an active system amplifier with a phase obtained through passage of a connection path passing through a stand-by system amplifier. In this technology, the path length is determined based on the electric length, and hence the effect can be obtained only when a signal having a specific wavelength is input. The effect cannot be obtained when a signal having a wavelength other than the specific wavelength is input.